Evaluation of viscosity values for. mixing and compaction temperatures

For many years, ASTM D 2493 has been used as a reference for determining mixing and compaction temperatures for asphalt binders. However, this method only applies to neat or unmodified binders. With the inception of modified binders, which incorporate various additives that stiffen binders, this method predicts unreasonably high mixing and compaction temperatures. The current study examined 50 commercially available binders. In this study, the viscosity values that are used for temperature selection were evaluated. Modified binders that are currently in industry are stiff, which makes it not possible to achieve reasonable temperatures using the current viscosity values. Therefore it was necessary to determine more appropriate viscosity ranges. Based on testing done with these binders, more reasonable viscosity ranges, centered on values of 0.275 and 0.550 Pa s, were chosen. The new viscosity range, coupled with a higher shear rate of 500 s(-1), resulted in more reasonable mixing and compaction temperatures that were from 13 to 52 degrees C lower than the traditional method.